/*-------------------------------------------------------------------------
 *
 * joinrels.c--
 *    Routines to determine which relations should be joined
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /usr/local/cvsroot/postgres95/src/backend/optimizer/path/joinrels.c,v 1.1.1.1 1996/07/09 06:21:36 scrappy Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "nodes/pg_list.h"
#include "nodes/relation.h"

#include "optimizer/internal.h"
#include "optimizer/cost.h"
#include "optimizer/paths.h"
#include "optimizer/tlist.h"
#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"


static List *find_clause_joins(Query *root, Rel *outer_rel, List *joininfo_list);
static List *find_clauseless_joins(Rel *outer_rel, List *inner_rels);
static Rel *init_join_rel(Rel *outer_rel, Rel *inner_rel, JInfo *joininfo);
static List *new_join_tlist(List *tlist, List *other_relids,
				int first_resdomno);
static List *new_joininfo_list(List *joininfo_list, List *join_relids);
static void add_superrels(Rel *rel, Rel *super_rel);
static bool nonoverlap_rels(Rel *rel1, Rel *rel2);
static bool nonoverlap_sets(List *s1, List *s2);
static void set_joinrel_size(Rel *joinrel, Rel *outer_rel, Rel *inner_rel,
			     JInfo *jinfo);

/*    
 * find-join-rels--
 *    Find all possible joins for each of the outer join relations in
 *    'outer-rels'.  A rel node is created for each possible join relation,
 *    and the resulting list of nodes is returned.  If at all possible, only
 *    those relations for which join clauses exist are considered.  If none
 *    of these exist for a given relation, all remaining possibilities are
 *    considered.
 *    
 * 'outer-rels' is the list of rel nodes
 *    
 * Returns a list of rel nodes corresponding to the new join relations.
 */
List *
find_join_rels(Query *root, List *outer_rels)
{
    List *joins = NIL;
    List *join_list = NIL;
    List *r = NIL;
    
    foreach(r, outer_rels) {
	Rel *outer_rel = (Rel *)lfirst(r);

	if(!(joins = find_clause_joins(root, outer_rel,outer_rel->joininfo)))
	    if (BushyPlanFlag)
		joins = find_clauseless_joins(outer_rel,outer_rels);
	    else
		joins = find_clauseless_joins(outer_rel,root->base_relation_list_);

	join_list = nconc(join_list, joins);
    }

    return(join_list);
}

/*    
 * find-clause-joins--
 *    Determines whether joins can be performed between an outer relation
 *    'outer-rel' and those relations within 'outer-rel's joininfo nodes
 *    (i.e., relations that participate in join clauses that 'outer-rel'
 *    participates in).  This is possible if all but one of the relations
 *    contained within the join clauses of the joininfo node are already
 *    contained within 'outer-rel'.
 *
 * 'outer-rel' is the relation entry for the outer relation
 * 'joininfo-list' is a list of join clauses which 'outer-rel' 
 * 	participates in
 *    
 * Returns a list of new join relations.
 */
static List *
find_clause_joins(Query *root, Rel *outer_rel, List *joininfo_list)
{
    List *join_list = NIL;
    List *i = NIL;
    
    foreach (i, joininfo_list) {
	JInfo *joininfo = (JInfo*)lfirst(i);
	Rel *rel;

	if(!joininfo->inactive) {
	    List *other_rels = joininfo->otherrels;

	    if(other_rels != NIL) {
		if(length(other_rels) == 1) {
		    rel = init_join_rel(outer_rel,
					get_base_rel(root, lfirsti(other_rels)),
					joininfo);
		} else if (BushyPlanFlag) {
		    rel = init_join_rel(outer_rel,
					get_join_rel(root, other_rels),
					joininfo);
		} else {
		    rel = NULL;
		}

		if (rel != NULL)
		    join_list = lappend(join_list, rel);
	    }
	}
    }

    return(join_list);
}

/*    
 * find-clauseless-joins--
 *    Given an outer relation 'outer-rel' and a list of inner relations
 *    'inner-rels', create a join relation between 'outer-rel' and each
 *    member of 'inner-rels' that isn't already included in 'outer-rel'.
 *    
 * Returns a list of new join relations.
 */
static List *
find_clauseless_joins(Rel *outer_rel, List *inner_rels)
{
    Rel *inner_rel;
    List *t_list = NIL;
    List *temp_node = NIL;
    List *i = NIL;
    
    foreach (i, inner_rels) {
	inner_rel = (Rel *)lfirst(i);
	if(nonoverlap_rels(inner_rel, outer_rel)) {
	    temp_node = lcons(init_join_rel(outer_rel, 
					   inner_rel,
					   (JInfo*)NULL),
			     NIL);
	    t_list = nconc(t_list,temp_node);
	} 
    }

    return(t_list);
}

/*    
 * init-join-rel--
 *    Creates and initializes a new join relation.
 *    
 * 'outer-rel' and 'inner-rel' are relation nodes for the relations to be
 * 	joined
 * 'joininfo' is the joininfo node(join clause) containing both
 * 	'outer-rel' and 'inner-rel', if any exists
 *    
 * Returns the new join relation node.
 */
static Rel *
init_join_rel(Rel *outer_rel, Rel *inner_rel, JInfo *joininfo)
{
    Rel *joinrel = makeNode(Rel);
    List *joinrel_joininfo_list = NIL;
    List *new_outer_tlist;
    List *new_inner_tlist;
    
    /*
     * Create a new tlist by removing irrelevant elements from both
     * tlists of the outer and inner join relations and then merging
     * the results together.
     */
    new_outer_tlist = 
	new_join_tlist(outer_rel->targetlist,   /*   XXX 1-based attnos */
		       inner_rel->relids, 1);
    new_inner_tlist = 
	new_join_tlist(inner_rel->targetlist,   /*   XXX 1-based attnos */
		       outer_rel->relids,
		       length(new_outer_tlist) + 1);
    
    joinrel->relids = NIL;
    joinrel->indexed = false;
    joinrel->pages = 0;
    joinrel->tuples = 0;
    joinrel->width = 0;
/*    joinrel->targetlist = NIL;*/
    joinrel->pathlist = NIL;
    joinrel->unorderedpath = (Path *)NULL;
    joinrel->cheapestpath = (Path *)NULL;
    joinrel->pruneable = true;
    joinrel->classlist = NULL;
    joinrel->relam = InvalidOid;
    joinrel->ordering = NULL;
    joinrel->clauseinfo = NIL;
    joinrel->joininfo = NULL;
    joinrel->innerjoin = NIL;
    joinrel->superrels = NIL;

    joinrel->relids = lcons(outer_rel->relids, /* ??? aren't they lists? -ay */
			   lcons(inner_rel->relids, NIL));

    new_outer_tlist = nconc(new_outer_tlist,new_inner_tlist);
    joinrel->targetlist = new_outer_tlist;
    
    if (joininfo) {
	joinrel->clauseinfo = joininfo->jinfoclauseinfo;
	if (BushyPlanFlag)
	  joininfo->inactive = true;
    }
    
    joinrel_joininfo_list = 
	new_joininfo_list(append(outer_rel->joininfo, inner_rel->joininfo),
			  intAppend(outer_rel->relids, inner_rel->relids));
    
    joinrel->joininfo = joinrel_joininfo_list;

    set_joinrel_size(joinrel, outer_rel, inner_rel, joininfo);
		     
    return(joinrel);
}

/*    
 * new-join-tlist--
 *    Builds a join relations's target list by keeping those elements that 
 *    will be in the final target list and any other elements that are still 
 *    needed for future joins.  For a target list entry to still be needed 
 *    for future joins, its 'joinlist' field must not be empty after removal 
 *    of all relids in 'other-relids'.
 *    
 * 'tlist' is the target list of one of the join relations
 * 'other-relids' is a list of relids contained within the other
 *    		join relation
 * 'first-resdomno' is the resdom number to use for the first created
 *    		target list entry
 *    
 * Returns the new target list.
 */
static List *
new_join_tlist(List *tlist,
	       List *other_relids,
	       int first_resdomno)
{
    int resdomno = first_resdomno - 1;
    TargetEntry *xtl = NULL;
    List *temp_node = NIL;
    List *t_list = NIL;
    List *i = NIL;
    List *join_list = NIL;
    bool in_final_tlist =false;
    
    
    foreach(i,tlist) {
	xtl= lfirst(i);
	in_final_tlist = (join_list==NIL);
	if( in_final_tlist)  {
	    resdomno += 1;
	    temp_node = 
		lcons(create_tl_element(get_expr(xtl),
				       resdomno),
		     NIL);
	    t_list = nconc(t_list,temp_node);
	} 
    }

    return(t_list);
}

/*    
 * new-joininfo-list--
 *    Builds a join relation's joininfo list by checking for join clauses
 *    which still need to used in future joins involving this relation.  A
 *    join clause is still needed if there are still relations in the clause
 *    not contained in the list of relations comprising this join relation.
 *    New joininfo nodes are only created and added to
 *    'current-joininfo-list' if a node for a particular join hasn't already
 *    been created.
 *
 * 'current-joininfo-list' contains a list of those joininfo nodes that 
 * 	have already been built 
 * 'joininfo-list' is the list of join clauses involving this relation
 * 'join-relids' is a list of relids corresponding to the relations 
 * 	currently being joined
 *    
 * Returns a list of joininfo nodes, new and old.
 */
static List *
new_joininfo_list(List *joininfo_list, List *join_relids)
{
    List *current_joininfo_list = NIL;
    List *new_otherrels = NIL;
    JInfo *other_joininfo = (JInfo*)NULL;
    List *xjoininfo = NIL;
    
    foreach (xjoininfo, joininfo_list) {
	JInfo *joininfo = (JInfo*)lfirst(xjoininfo);

	new_otherrels = joininfo->otherrels;
	if (nonoverlap_sets(new_otherrels,join_relids)) {
	    other_joininfo = joininfo_member(new_otherrels,
					     current_joininfo_list);
	    if(other_joininfo) {
		other_joininfo->jinfoclauseinfo =
		    (List*)LispUnion(joininfo->jinfoclauseinfo,
				     other_joininfo->jinfoclauseinfo);
	    }else {
		other_joininfo = makeNode(JInfo);

		other_joininfo->otherrels =
		    joininfo->otherrels;
		other_joininfo->jinfoclauseinfo =
		    joininfo->jinfoclauseinfo;
		other_joininfo->mergesortable =
		    joininfo->mergesortable;
		other_joininfo->hashjoinable =
		    joininfo->hashjoinable;
		other_joininfo->inactive = false;
					   
		current_joininfo_list = lcons(other_joininfo,
					     current_joininfo_list);
	    }
	}
    }

    return(current_joininfo_list);
}

/*
 * add-new-joininfos--
 *    For each new join relation, create new joininfos that
 *    use the join relation as inner relation, and add
 *    the new joininfos to those rel nodes that still
 *    have joins with the join relation.
 *
 * 'joinrels' is a list of join relations.
 *
 * Modifies the joininfo field of appropriate rel nodes.
 */
void
add_new_joininfos(Query *root, List *joinrels, List *outerrels)
{
    List *xjoinrel = NIL;
    List *xrelid = NIL;
    List *xrel = NIL;
    List *xjoininfo = NIL;
    
    foreach(xjoinrel, joinrels) {
	Rel *joinrel = (Rel *)lfirst(xjoinrel);
        foreach(xrelid, joinrel->relids) {
	    Relid relid = (Relid)lfirst(xrelid);
	    Rel *rel = get_join_rel(root, relid);
	    add_superrels(rel,joinrel);
	}
    }
    foreach(xjoinrel, joinrels) {
	Rel *joinrel = (Rel *)lfirst(xjoinrel);

	foreach(xjoininfo, joinrel->joininfo) {
	    JInfo *joininfo = (JInfo*)lfirst(xjoininfo);
	    List *other_rels = joininfo->otherrels;
	    List *clause_info = joininfo->jinfoclauseinfo;
	    bool mergesortable = joininfo->mergesortable;
	    bool hashjoinable = joininfo->hashjoinable;

	    foreach(xrelid, other_rels) {
		Relid relid = (Relid)lfirst(xrelid);
		Rel *rel = get_join_rel(root, relid);
		List *super_rels = rel->superrels;
		List *xsuper_rel = NIL;
		JInfo *new_joininfo = makeNode(JInfo);
						
		new_joininfo->otherrels = joinrel->relids;
		new_joininfo->jinfoclauseinfo = clause_info;
		new_joininfo->mergesortable = mergesortable;
		new_joininfo->hashjoinable = hashjoinable;
		new_joininfo->inactive = false;
		rel->joininfo = 
		    lappend(rel->joininfo, new_joininfo);

		foreach(xsuper_rel, super_rels) {
		    Rel *super_rel = (Rel *)lfirst(xsuper_rel);

		    if( nonoverlap_rels(super_rel,joinrel) ) {
			List *new_relids = super_rel->relids;
			JInfo *other_joininfo = 
			    joininfo_member(new_relids,
					    joinrel->joininfo);

			if (other_joininfo) {
			    other_joininfo->jinfoclauseinfo =
				(List*)LispUnion(clause_info,
						 other_joininfo->jinfoclauseinfo);
			} else {
			    JInfo *new_joininfo = makeNode(JInfo);

			    new_joininfo->otherrels = new_relids;
			    new_joininfo->jinfoclauseinfo = clause_info; 
			    new_joininfo->mergesortable = mergesortable;
			    new_joininfo->hashjoinable = hashjoinable;
			    new_joininfo->inactive = false;
			    joinrel->joininfo =
				lappend(joinrel->joininfo,
					 new_joininfo);
			}
		    }
		}
	    }
	}
    }
    foreach(xrel, outerrels)  {
	Rel *rel = (Rel *)lfirst(xrel);
	rel->superrels = NIL;
    }
}

/*
 * final-join-rels--
 *     Find the join relation that includes all the original
 *     relations, i.e. the final join result.
 *
 * 'join-rel-list' is a list of join relations.
 *
 * Returns the list of final join relations.
 */
List *
final_join_rels(List *join_rel_list)
{
    List *xrel = NIL;
    List *temp = NIL;
    List *t_list = NIL;
    
    /*
     * find the relations that has no further joins,
     * i.e., its joininfos all have otherrels nil.
     */
    foreach(xrel,join_rel_list)  {
	Rel *rel = (Rel *)lfirst(xrel);
	List *xjoininfo = NIL;
	bool final = true;

	foreach (xjoininfo, rel->joininfo) {
	    JInfo *joininfo = (JInfo*)lfirst(xjoininfo);

	    if (joininfo->otherrels != NIL)  {
		final = false;
		break;
	    }
	}
	if (final)  {
	    temp = lcons(rel, NIL);
	    t_list = nconc(t_list, temp);
	}
    }

    return(t_list);
}

/*
 * add_superrels--
 *    add rel to the temporary property list superrels.
 *
 * 'rel' a rel node
 * 'super-rel' rel node of a join relation that includes rel
 *
 * Modifies the superrels field of rel
 */
static void
add_superrels(Rel *rel, Rel *super_rel)
{
    rel->superrels = lappend(rel->superrels, super_rel);
}

/*
 * nonoverlap-rels--
 *    test if two join relations overlap, i.e., includes the same
 *    relation.
 *
 * 'rel1' and 'rel2' are two join relations
 *
 * Returns non-nil if rel1 and rel2 do not overlap.
 */
static bool
nonoverlap_rels(Rel *rel1, Rel *rel2)
{
    return(nonoverlap_sets(rel1->relids, rel2->relids));
}

static bool
nonoverlap_sets(List *s1, List *s2)
{
    List *x = NIL;
    
    foreach(x,s1)  {
	int e = lfirsti(x);
	if(intMember(e,s2))
	    return(false);
    }
    return(true);
}

static void
set_joinrel_size(Rel *joinrel, Rel *outer_rel, Rel *inner_rel, JInfo *jinfo)
{
    int ntuples;
    float selec;

    /* voodoo magic. but better than a size of 0. I have no idea why
       we didn't set the size before. -ay 2/95 */
    if (jinfo==NULL) {
	/* worst case: the cartesian product */
	ntuples = outer_rel->tuples * inner_rel->tuples;
    } else {
	selec = product_selec(jinfo->jinfoclauseinfo);
/*	ntuples = Min(outer_rel->tuples,inner_rel->tuples) * selec; */
	ntuples = outer_rel->tuples * inner_rel->tuples  * selec;
    }
    
    /* I bet sizes less than 1 will screw up optimization so
       make the best case 1 instead of 0  - jolly*/
    if (ntuples < 1) 
	ntuples = 1;

    joinrel->tuples = ntuples;
}
